Apparatus for monitoring the approach of two relatively movable parts

Abstract

An arrangement for monitoring first and second relatively movable parts in which an actuator is connected to one of the first and second parts. The actuator includes a transponder. A sensor is connected to the other one of the two parts and has a receiver circuit with a receiver coil. A reduction coil is arranged so that its magnetic field can reduce a magnetic field of the receiver coil in a predetermined manner. The transponder touchlessly transmits a bit-coded transponder signal to the sensor when a distance between the actuator and the sensor falls below a predetermined value, and the receiver circuit compares the transponder signal to a stored bit sample for generating a monitoring output signal.

1 . Apparatus for monitoring first and second relatively movable parts comprising an actuator connected to one of the first and second parts and including a transponder, 
 a sensor connected to the other one of the first and second parts and including a receiver circuit with a receiver coil, and a reduction coil which is arranged so that its magnetic field reduces a magnetic field of the receiver coil in a predetermined manner,    the transponder being adapted to touchlessly transmit a bit-coded transponder signal to the sensor when a distance between the actuator and the sensor falls below a predetermined value,    wherein the receiver circuit being adapted to compare the transponder signal to a stored bit sample for generating a monitoring output signal.    
   
   
       2 . Apparatus according to  claim 1  wherein the receiver coil and the reduction coil are subjected to opposing phases.  
   
   
       3 . Apparatus according to  claim 1  wherein a strength of the magnetic field of the reduction coil is adjustable.  
   
   
       4 . Apparatus according to  claim 3  wherein the strength of the magnetic field of the reduction coil is adjustable with one of an adjustable resistor and a FET transistor.  
   
   
       5 . Apparatus according to  claim 1  including a switching element for controlling the reduction coil.  
   
   
       6 . Apparatus according to  claim 5  wherein the switching element comprises a semiconductor element.  
   
   
       7 . Apparatus according to  claim 1  wherein the reduction coil is integrated into the receiver circuit.  
   
   
       8 . Apparatus according to  claim 1  including a voltage source for the reduction coil which is independent of the receiver circuit.  
   
   
       9 . Apparatus according to  claim 1  including a common magnetic core, and wherein the receiver coil and the reduction coil are arranged on the common magnet core.  
   
   
       10 . Apparatus according to  claim 1  wherein the first and second parts comprise a door and a door frame, respectively.